You probably already have a Calibre shurtcut (on the desktop or in the menu).
Copy this shortcut so you have two of them. Go in the properties, you will see the shortcut point to the calibre executable. At the end of the calibre executable add:
On the first shortcut:
--with-library C:\Ebook-english
On the second:
--with-library C:\Ebook-french
P.S. Change the path to your 2 folder.

Rename the 2 shortcut in function of the path you put.
This should do it!